Pattern formation method and method for forming semiconductor device

ABSTRACT

A pattern formation method includes the steps of forming a flowable film made of a material with flowability; forming at least one of a concave portion and a convex portion provided on a pressing face of a pressing member onto the flowable film by pressing the pressing member against the flowable film; forming a solidified film by solidifying the flowable film, onto which the at least one of a concave portion and a convex portion has been transferred, through annealing at a first temperature with the pressing member pressed against the flowable film; and forming a pattern made of the solidified film burnt by annealing at a second temperature higher than the first temperature.

BACKGROUND OF THE INVENTION

In a method for forming multilayered interconnects in formation processfor semiconductor devices, with respect to a generation of a design ruleof 130 nm or less, a damascene method in which a concave portion (a viahole or an interconnect groove) is formed in an insulating film, theconcave portion is filled with a metal film principally by a metalplating method and the metal film is planarized by chemical mechanicalpolishing (CMP) is employed for forming a buried interconnect. In thiscase, as a method for forming a concave portion in an insulating film,apart from conventionally known dry etching, nano-imprint lithographyproposed by S. Y. Chou, et al. in Non-patent Document 1 (Applied PhysicsLetter, Volume 67 (1995), pp. 3114-3116) or Patent Document 1 (U.S. Pat.No. 5,772,905 (Jun. 30, 1998)) is known.

Now, a conventional pattern formation method by using the nano-imprintlithography will be described with reference to FIGS. 17A through 17E.

First, as shown in FIG. 17A, a film 102A of a thermosetting resin isformed on a substrate (semiconductor wafer) 101 in a surface portion ofwhich devices such as transistors and interconnects (not shown in thedrawing) have been formed, and thereafter, as shown in FIG. 17B, apressing face of a mold 103 having a convex portion 104 on the pressingface is pressed against the film 102A, so as to transfer the convexportion 104 of the mold 103 onto the film 102A.

Next, as shown in FIG. 17C, with a pressure applied to the mold 103, thesubstrate 101 is annealed for curing the film 102A, so as to form acured film 102B. In the case where the film 102A is made of aphoto-setting resin, the cured film 102B is formed through irradiationwith light of UV or the like with a pressure applied to the mold 103.

Then, as shown in FIG. 17D, the mold 103 is moved away from the curedfilm 102B, and thus, a concave portion 105 is formed in the cured film102B through the transfer of the convex portion 104 of the mold 103.

Next, the whole cured film 102B is subjected to anisotropic dry etching(anisotropic etch back), so as to remove a portion of the cured film102B remaining on the bottom of the concave portion 105 as shown in FIG.17E.

S. Y. Chou et al. use PMMA (polymethyl methacrylate), that is, a resistmaterial, as the material for the film 102A, and after curing the PMMAonce, the concave portion 105 is formed by pressing the mold 103 againstthe film 102A with the PMMA slightly softened through annealing at 200°C. In this case, since the PMMA has been cured, a high pressure as highas 140 atmospheric pressures is disadvantageously necessary for formingthe concave portion 105.

Therefore, in order to overcome this disadvantage, according to PatentDocument 2 (Japanese Laid-Open Patent Publication No. 2000-194142), aphoto-setting material film made of a liquid photo-setting material isused as the film 102A and the film 102A is cured through annealing andlight irradiation with the mold 103 pressed against the film 102A. Thus,the applied pressure is reduced to several atmospheric pressures, andhence, the accuracy in horizontal positions of the mold 103 and thesubstrate 101 is improved.

At this point, a method for forming a buried interconnect included inmultilayered interconnects by the damascene method will be described. Ingeneral, a method for forming a buried plug or a buried interconnect.alone by the damascene method is designated as a single damascenemethod, and a method for forming both a buried plug and a buriedinterconnect simultaneously by the damascene method is designated as adual damascene method.

Now, a formation method for a semiconductor device in which a plug or ametal interconnect is formed by the single damascene method will bedescribed with reference to FIGS. 18A through 18E.

First, as shown in FIG. 18A, an insulating film 112 of, for example, asilicon oxide film is formed on a substrate (semiconductor wafer) 111by, for example, a chemical vapor deposition (CVD) method or a spin ondielectric (SOD) method.

Next, as shown in FIG. 18B, a resist pattern 113 having an opening forforming a via hole or an interconnect groove is formed on the insulatingfilm 112 by lithography. Thereafter, as shown in FIG. 18C, theinsulating film 112 is dry etched by using the resist pattern 113 as amask, thereby forming a concave portion 114 corresponding to a via holeor an interconnect groove in the insulating film 112.

Then, as shown in FIG. 18D, after forming a barrier metal layer (notshown in the drawing) by, for example, a sputtering method, a copperfilm 115 is deposited on the barrier metal layer by, for example, aplating method.

Next, as shown in FIG. 18E, an unnecessary portion of the copper film115, namely, a portion thereof exposed above the insulating film 112, isremoved by chemical mechanical polishing (CMP), so as to form a plug ormetal interconnect 116 made of the copper film 115.

Now, a formation method for a semiconductor device in which a plug and ametal interconnect are formed by the dual damascene method will bedescribed with reference to FIGS. 19A through 19D and 20A through 20D.Herein, a process in which a plug and a metal interconnect are formed byforming a via hole before forming an interconnect groove and filling ametal film in the via hole and the interconnect groove, namely, what iscalled via first process, will be described.

First, as shown in FIG. 19A, an insulating film 122 of, for example, asilicon oxide film is formed on a substrate (semiconductor wafer) 121by, for example, the chemical vapor deposition method or the spin ondielectric method.

Next, as shown in FIG. 19B, a first resist pattern 123 having an openingfor forming a via hole is formed on the insulating film 122 by thelithography, and thereafter, as shown in FIG. 19C, the insulating film122 is dry etched by using the first resist pattern 123 as a mask,thereby forming a via hole 124 in the insulating film 122.

Then, as shown in FIG. 19D, after forming a bottom antireflectioncoating (BARC) 125 on the insulating film 122 including the inside ofthe via hole 124, a second resist pattern 126 having an opening forforming an interconnect groove is formed on the bottom antireflectioncoating 125.

Next, as shown in FIG. 20A, the bottom antireflection coating 125 is dryetched by using the second resist pattern 126 as a mask, so as to allowa portion of the bottom antireflection coating 125 to remain in a lowerportion of the via hole 124. Thereafter, the insulating film 122 is dryetched by using the second resist pattern 126 and the bottomantireflection coating 125 as a mask, thereby forming an interconnectgroove 127 in the insulating film 122.

Subsequently, as shown in FIG. 20B, after removing the second resistpattern 126 and the bottom antireflection coating 125 by ashing andcleaning, a barrier metal layer (not shown in the drawing) is formed bythe sputtering method. Thereafter, as shown in FIG. 20C, a copper film128 is deposited on the barrier metal layer by the plating method, so asto fill the via hole 124 and the interconnect groove 127 with the copperfilm 128.

Next, an unnecessary portion of the copper film 128, namely, a portionthereof exposed above the insulating film 122, is removed by thechemical mechanical polishing. Thus, as shown in FIG. 20D, a plug 130and a metal interconnect 131 made of the copper film 128 are formed atthe same time.

SUMMARY OF THE INVENTION

An object of the invention is forming a pattern with a uniform structureof the basic skeleton and improved film quality in a small number ofprocesses.

In order to achieve the object, the pattern formation method of thisinvention includes the steps of forming a flowable film made of amaterial with flowability; forming at least one of a concave portion anda convex portion provided on a pressing face of a pressing member ontothe flowable film by pressing the pressing member against the flowablefilm; forming a solidified film by solidifying the flowable film, ontowhich the at least one of a concave portion and a convex portion hasbeen transferred, through annealing of the flowable film at a firsttemperature with the pressing member pressed against the flowable film;and forming a pattern made of the solidified film burnt by annealing ata second temperature higher than the first temperature.

In the pattern formation method of this invention, after forming, ontothe flowable film, at least one of the concave portion and the convexportion provided on the pressing face of the pressing member, thepattern is formed by solidifying and burning the flowable film.Therefore, the pattern can be formed through a small number ofprocesses. Also, in the step of forming the solidified film by formingat least one of the concave portion and the convex portion onto theflowable film by pressing the pressing face of the pressing memberagainst the flowable film, the annealing is performed at the firsttemperature that is a relatively low temperature, and thus, the basicskeleton of the solidified film (such as a polymer skeleton of anorganic film, a siloxane skeleton of a silicon oxide film or anorganic-inorganic film, or a resin skeleton of a resist film) is formed.Thereafter, in the step of forming the pattern, the annealing isperformed at the second temperature that is a relatively hightemperature, so as to vaporize porogen such as an acrylic polymer, aremaining solvent or the like from the solidified film. Therefore, ascompared with the case where formation of a basic skeleton andvaporization of the porogen, a remaining solvent or the like areperformed in parallel, the structure of the basic skeleton of thepattern is made uniform, resulting in improving the film quality of thepattern. Accordingly, in the case where the pattern is made of aninsulating film, the dielectric constant is uniform within the wholefilm, and the insulating film attains high reliability.

In the pattern formation method of this invention, the first temperatureis preferably approximately 150° C. through approximately 300° C.

Thus, the basic skeleton of the flowable film can be formed withoutvaporizing the porogen or the like included in the flowable film.

In the pattern formation method of this invention, the secondtemperature is preferably approximately 350° C. through approximately450° C.

Thus, the porogen or the like can be vaporized from the solidified filmwithout degrading the film quality of the solidified film and also thefilm quality of the pattern.

In the pattern formation method of this invention, the material withflowability may be an insulating material.

In the pattern formation method of this invention, the material withflowability is preferably in the form of a liquid or a gel.

Thus, the flowable film can be easily and definitely formed.

In the pattern formation method of this invention, in the step offorming a flowable film, the flowable film is preferably formed on asubstrate by supplying the material with flowability onto the substraterotated.

Thus, the thickness of the flowable film can be made uniform.

In the pattern formation method of this invention, in the step offorming a flowable film, the flowable film is preferably formed on asubstrate by supplying the material with flowability onto the substrateand rotating the substrate after the supply.

Thus, the thickness of the flowable film can be made uniform.

In the pattern formation method of this invention, in the step offorming a flowable film, the flowable film is preferably formed on asubstrate by supplying, in the form of a shower or a spray, the materialwith flowability onto the substrate rotated.

Thus, the flowable film with a comparatively small thickness can bedefinitely formed.

In the pattern formation method of this invention, in the step offorming a flowable film, the flowable film is preferably formed on asubstrate by supplying the material with flowability from a fine sprayvent of a nozzle onto the substrate with the nozzle having the finespray vent and the substrate relatively moved along plane directions.

Thus, the thickness of the flowable film can be controlled to be adesired thickness by adjusting the relative moving rates of the nozzleand the substrate. Also, the degree of the flowability of the flowablefilm can be changed by adjusting the viscosity of the material withflowability. Furthermore, the process speed can be controlled byadjusting the number of nozzles.

In the pattern formation method of this invention, in the step offorming a flowable film, the flowable film is preferably formed on asubstrate by supplying the material with flowability having been adheredto a surface of a roller onto the substrate with the roller rotated.

Thus, the thickness of the flowable film can be controlled by adjustinga distance between the roller and the substrate and a force for pressingthe roller against the substrate. Also, a material with flowability andhigh viscosity can be used.

The pattern formation method of this invention preferably furtherincludes, between the step of forming a flowable film and the step offorming at least one of a concave portion and a convex portion onto theflowable film, a step of selectively removing a peripheral portion ofthe flowable film.

Thus, the peripheral portion of the substrate can be mechanically heldin the process for forming the pattern with ease.

In the case where the pattern formation method of this inventionincludes the step of selectively removing a peripheral portion of theflowable film, this step is preferably performed by supplying a solutionfor dissolving the material with flowability onto the peripheral portionof the flowable film with the flowable film rotated.

Thus, the flowable film can be definitely removed from a peripheralportion of a substrate in the plane shape of a circle or a polygon witha large number of vertexes.

In the case where the pattern formation method of this inventionincludes the step of selectively removing a peripheral portion of theflowable film, this step is preferably performed by modifying theperipheral portion of the flowable film through irradiation with lightand removing the modified peripheral portion.

Thus, the flowable film can be definitely removed from a peripheralportion of a substrate not only in the plane shape of a circle or apolygon with a large number of vertexes but also in the shape of apolygon with a small number of vertexes such as a triangle or arectangle.

In the pattern formation method of this invention, it is preferred thatthe flowable film is formed on a substrate, and that in the step offorming at least one of a concave portion and a convex portion onto theflowable film, a plurality of distances between a surface of thesubstrate and the pressing face are measured, and the flowable film ispressed with the pressing face in such a manner that the plurality ofdistances are equal to one another.

In the case where a plurality of distances between the surface of thesubstrate or the stage and the pressing face are measured in the patternformation method of this invention, the plurality of distances arepreferably measured by measuring capacitance per unit area in respectivemeasurement positions.

Thus, the plural distances can be easily and definitely measured.

Thus, a distance of the surface of the flowable film from the surface ofthe substrate can be always made uniform, and therefore, an operationfor making uniform a distance between the surface of the substrate andthe pressing face of the pressing member every given period of time canbe omitted.

In the pattern formation method of this invention, it is preferred thatthe flowable film is formed on a substrate, and that in the step offorming at least one of a concave portion and a convex portion onto theflowable film, a plurality of distances between a surface of a stagewhere the substrate is placed and the pressing face are measured, andthe flowable film is pressed with the pressing face in such a mannerthat the plurality of distances are equal to one another.

Thus, a distance of the surface of the flowable film from the surface ofthe substrate can be always made uniform, and therefore, an operationfor making uniform a distance between the surface of the substrate andthe pressing face of the pressing member every given period of time canbe omitted.

In the pattern formation method of this invention, the pressing face ofthe pressing member preferably has a hydrophobic property.

Thus, the pressing member can be easily moved away from the solidifiedfilm, and hence, a pattern with fewer defects can be formed.

In the pattern formation method of this invention, it is preferred thatthe material with flowability is a photo-setting resin, and that thestep of forming a solidified film includes a sub-step of irradiating theflowable film with light.

Thus, the flowable film can be easily and rapidly solidified through aphotochemical reaction and a thermal chemical reaction.

In the pattern formation method of this invention, the material withflowability may be an organic material, an inorganic material, anorganic-inorganic material, a photo-setting resin or a photosensitiveresin.

In the pattern formation method of this invention, the pattern ispreferably a porous film.

Thus, a pattern with a low dielectric constant can be formed.

In the pattern formation method of this invention, in the step offorming a pattern, the solidified film is preferably annealed at thesecond temperature with the pressing face pressed against the solidifiedfilm.

Thus, the shape of at least one of the concave portion and the convexportion formed in the solidified film can be highly accurately kept.

In the pattern formation method of this invention, in the step offorming a pattern, the solidified film is preferably annealed at thesecond temperature with the pressing face moved away from the solidifiedfilm.

Thus, the porogen, the remaining solvent or the like included in thesolidified film can be easily vaporized.

The method for forming a semiconductor device of this invention includesthe steps of forming a flowable film made of an insulating material withflowability; forming a convex portion provided on a pressing face of apressing member onto the flowable film by pressing the pressing memberagainst the flowable film; forming a solidified film by solidifying theflowable film, onto which the convex portion has been transferred,through annealing at a first temperature with the pressing memberpressed against the flowable film; forming a pattern having a concaveportion in the shape corresponding to the convex portion and made of thesolidified film burnt by annealing at a second temperature higher thanthe first temperature; and forming at least one of a metal interconnectand a plug made of a metal material by filling the concave portion witha conductive material.

In the method for forming a semiconductor device of this invention, asdescribed with respect to the pattern formation method, after forming,onto the flowable film, the convex portion provided on the pressing faceof the pressing member, the pattern is formed by solidifying and burningthe flowable film. Therefore, the pattern can be formed through a smallnumber of processes. Also, in the step of forming the solidified film,the basic skeleton of the solidified film is formed, and thereafter, inthe step of forming the pattern, porogen such as an acrylic polymer, aremaining solvent or the like is vaporized from the solidified film.Therefore, the structure of the basic skeleton of the pattern is madeuniform, resulting in improving the film quality of the pattern.Accordingly, the dielectric constant of the insulating film of thepattern is made uniform in the whole film, so that the reliability ofthe insulating film and also the reliability of the semiconductor devicecan be improved.

In the case where the concave portion of the pattern corresponds to aninterconnect groove or a hole, a metal interconnect or a plug made ofthe metal material is formed by the single damascene method, and in thecase where the concave portion of the pattern corresponds to aninterconnect groove and a hole, a metal interconnect and a plug made ofthe metal material are formed by the dual damascene method.

In the method for forming a semiconductor device of this invention, thefirst temperature is preferably approximately 150° C. throughapproximately 300° C.

Thus, the basic skeleton of the flowable film can be formed withoutvaporizing the porogen or the like included in the flowable film.

In the method for forming a semiconductor device of this invention, thesecond temperature is preferably approximately 350° C. throughapproximately 450° C.

Thus, the porogen or the like can be vaporized from the solidified filmwithout degrading the film quality of the solidified film and also thefilm quality of the pattern.

In the method for forming a semiconductor device of this invention, itis preferred that the material with flowability is a photo-settingresin, and that the flowable film is solidified by irradiating theflowable film with light.

Thus, the flowable film can be easily and rapidly solidified through aphotochemical reaction and a thermal chemical reaction.

In the method for forming a semiconductor device of this invention, thematerial with flowability may be an organic material, an inorganicmaterial, an organic-inorganic material, a photo-setting resin or aphotosensitive resin.

In the method for forming a semiconductor device of this invention, inthe step of forming a pattern, the solidified film is preferablyannealed at the second temperature with the pressing face pressedagainst the solidified film.

Thus, the shape of irregularities formed in the solidified film can behighly accurately kept.

In the method for forming a semiconductor device of this invention, inthe step of forming a pattern, the solidified film is preferablyannealed at the second temperature with the pressing face moved awayfrom the solidified film.

Thus, the porogen, the remaining solvent or the like included in thesolidified film can be easily vaporized.

In the method for forming a semiconductor device of this invention, thepattern is preferably a porous film.

Thus, an insulating film made of the pattern with a low dielectricconstant can be formed.

In the method for forming a semiconductor device of this invention, thepattern preferably has a dielectric constant of approximately 4 or less.

Thus, the dielectric constant of the insulating film can be definitelylowered, so as to reduce capacitance between metal interconnects.

The method for forming a semiconductor device of this inventionpreferably further includes, after the step of forming a pattern andbefore the step of forming at least one of a metal interconnect and aplug, a step of removing a portion of the pattern remaining on a bottomof the concave portion by etching.

Thus, a hole or an interconnect groove made of the concave portion freefrom a remaining portion in the bottom thereof can be realized.

Furthermore, this invention provides one solution for the problem thatthe cost of the formation process for the semiconductor device is highbecause the number of processes is large, when multilayeredinterconnects are formed by the damascene method.

In another way, the nano-imprint lithography is applied instead of acombination of the resist pattern formation by the lithography and thedry etching, so as to reduce the number of processes for lowering thecost, in the process for forming a concave portion (a via hole or aninterconnect groove) in an insulating film.

In the case where the nano-imprint lithography is applied to aninsulating film to be used as an interlayer insulating film, in order tosecure stability of the insulating film in semiconductor formationprocess performed thereafter, a process for curing the insulatingmaterial by annealing it at a temperature of approximately 400° C. isgenerally necessary.

The conventional nano-imprint lithography is, however, carried out forforming a resist pattern, and hence, the annealing temperature isapproximately 200° C. at most.

If the insulating material is annealed at a temperature of approximately350° C. or more for applying the insulating film to the nano-imprintlithography for forming a concave portion, the structure of the basicskeleton of the insulating film becomes locally ununiform, and hence,the film quality is degraded in such a manner that the dielectricconstant of the insulating film is locally varied.

Therefore, this invention provides one solution for the problem that theperformance and the reliability of the semiconductor device are largelydegraded because of insufficient reliability of an insulating film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A through 1E are cross-sectional views for showing procedures ina pattern formation method according to Embodiment 1.

FIGS. 2A through 2E are cross-sectional views for showing procedures ina pattern formation method according to Embodiment 2.

FIG. 3A is a flowchart for showing a sequence of a conventional patternformation method and FIG. 3B is a flowchart for showing a sequence ofthe pattern formation method of Embodiment 1 or 2.

FIGS. 4A through 4C are cross-sectional views for showing procedures inExample 1 employed in the pattern formation method of Embodiment 1 or 2.

FIGS. 5A and 5B are cross-sectional views for showing procedures inExample 2 employed in the pattern formation method of Embodiment 1 or 2.

FIGS. 6A and 6B are cross-sectional views for showing procedures inExample 3 employed in the pattern formation method of Embodiment 1 or 2.

FIGS. 7A and 7B are cross-sectional views for showing procedures inExample 4 employed in the pattern formation method of Embodiment 1 or 2.

FIGS. 8A through 8C are cross-sectional views for showing procedures ina pattern formation method according to Embodiment 3.

FIGS. 9A through 9C are cross-sectional views for showing otherprocedures in the pattern formation method of Embodiment 3.

FIGS. 10A and 10B are cross-sectional views for showing procedures in apattern formation method according to Embodiment 4.

FIGS. 11A and 11B are cross-sectional views for showing other proceduresin the pattern formation method of Embodiment 4.

FIGS. 12A and 12B are cross-sectional views for showing procedures in apattern formation method according to Embodiment 5.

FIGS. 13A through 13D are cross-sectional views for showing proceduresin a method for forming a semiconductor device according to Embodiment6.

FIGS. 14A through 14D are cross-sectional views for showing otherprocedures in the method for forming a semiconductor device ofEmbodiment 6.

FIGS. 15A through 15D are cross-sectional views for showing proceduresin a method for forming a semiconductor device according to Embodiment7.

FIGS. 16A through 16D are cross-sectional views for showing otherprocedures in the method for forming a semiconductor device ofEmbodiment 7.

FIGS. 17A through 17E are cross-sectional views for showing proceduresin a pattern formation method according to a first conventional example.

FIGS. 18A through 18E are cross-sectional views for showing proceduresin a method for forming a semiconductor device according to a secondconventional example.

FIGS. 19A through 19D are cross-sectional views for showing proceduresin a method for forming a semiconductor device according to a thirdconventional example.

FIGS. 20A through 20D are cross-sectional views for showing otherprocedures in the method for forming a semiconductor device of the thirdconventional example.

DESCRIPTION OF THE EMBODIMENTS

(Embodiment 1)

A pattern formation method. according to Embodiment 1 will now bedescribed with reference to FIGS. 1A through 1E.

First, as shown in FIG. 1A, a material with flowability, such as amaterial in the form of a liquid or a gel, is supplied onto a substrate11 of a semiconductor wafer, so as to form a film with flowability(hereinafter simply referred to as a flowable film) 12A. In general,annealing is performed at approximately 80° C. through 120° C. in orderto vaporize a part or most of a solvent included in the flowable film12A formed on the substrate 11. This annealing is generally designatedas pre-bake, and the temperature of the pre-bake may be set so that theflowability of the flowable film 12A can be kept in a transfer processsubsequently performed. Specifically, the temperature may be set inaccordance with the characteristics (such as the boiling point) of thesolvent used for supplying the material with flowability, and thepre-bake may be omitted in some cases.

The flowable film 12A may be, for example, an organic film, an inorganicfilm, an organic-inorganic film (organic-inorganic hybrid film), aphoto-setting resin film that is cured through irradiation with light, aphotosensitive resin film such as a resist film, a porous film having alarge number of pores with a diameter of approximately 1 nm through 10nm therein, or the like.

A method for forming the flowable film 12A may be a spin coating method,a microscopic spraying method, a rotation roller method or the like, thethickness of the flowable film 12A is adjusted differently dependingupon the employed method, and the film thickness can be adjusted byselecting the method for forming the flowable film 12A. The method forforming the flowable film 12A will be described in detail in Examples 1through 4 below.

The plane shape of the substrate 11 is not particularly specified andmay be any shape including a circle, a polygon and the like.

In the case where the flowable film 12A is used as an interlayer film ofmultilayered interconnects, the material with flowability is preferablyan insulating material.

Next, as shown in FIG. 1B, a pressing face of a pressing member 13,which has the flat pressing face with irregularities thereon, is opposedto the surface of the flowable film 12A, and thereafter, a pressuretoward the substrate is applied to the pressing member 13. Thus, theirregularities are transferred onto the surface of the flowable film 12Aand the whole top face of the flowable film 12A excluding thetransferred irregularities is planarized. In FIG. 1B, a referencenumeral 14 denotes a convex portion provided on the pressing face.

In this case, merely by pressing the flowable film 12A with the pressingface of the pressing member 13, the whole top face of the flowable film12A excluding the transferred irregularities is planarized. However,when the press with the pressing member 13 is intermitted, the flowablefilm 12A is changed into an energetically stable shape owing to thesurface tension of the flowable film 12A.

Therefore, as shown in FIG. 1C, with the pressing member 13 pressedagainst the flowable film 12A, the flowable film 12A is annealed at afirst temperature (T1) so as to cause a chemical reaction within theflowable film 12A. Thus, the flowable film 12A is solidified, therebyforming a solidified film 12B made of the flowable film 12A and havingthe transferred irregularities. The first temperature (T1) is preferablyapproximately 150° C. through approximately 300° C. and is morepreferably approximately 200° C. through approximately 250° C. In thismanner, the basic skeleton of the flowable film 12A, such as a polymerskeleton or a siloxane skeleton, is definitely formed. In thesolidifying process, the annealing is performed with a hot plate set toa desired temperature for approximately 2 through 3 minutes.

Next, as shown in FIG. 1D, with the pressing member 13 pressed againstthe solidified film 12B, the solidified film 12B is annealed at a secondtemperature (T2) higher than the first temperature (T1) for burning thesolidified film 12B. Thus, a pattern 12C made of the burnt solidifiedfilm 12B is formed. The second temperature (T2) is preferablyapproximately 350° C. through approximately 450° C. In this manner,porogen and the like are vaporized from the solidified film 12B wherethe basic skeleton has been formed, and hence, the pattern 12C with auniform film quality can be obtained. In the pattern formation process,the annealing is performed with a hot plate set to a desired temperaturefor approximately 2 through approximately 15 minutes.

Next, after lowering the temperature of the pattern 12C to a temperaturerange between approximately 100° C. and room temperature, the pressingmember 13 is moved away from the pattern 12C, and thereafter, thetemperature of the pattern 12C is ultimately lowered to roomtemperature. Thus, as shown in FIG. 1E, the pattern 12C that has aconcave portion 15 formed through the transfer of the convex portion 14of the pressing member 13 and is flat in the whole top face excludingthe concave portion 15 is obtained.

In order to provide the pressing face having the irregularities of thepressing member 13 with a hydrophobic property, the pressing face ispreferably subjected to a Teflon (registered trademark) coatingtreatment or a surface treatment with a silicon coupling material. Thus,the pressing member 13 can be easily moved away from the pattern 12C,and hence, the pattern 12C with fewer defects can be formed.

In the case where the irregularities provided on the pressing face ofthe pressing member 13 is a convex portion in the shape of a column(dot), a hole is formed in the pattern 12C, and in the case where it isa convex portion in the shape of a line, an interconnect groove isformed in the pattern 12C. On the contrary, in the case where theirregularities provided on the pressing face of the pressing member 13is a concave portion in the shape of a hole, a convex portion in theshape of a column (dot) is formed in the pattern 12C, and in the casewhere it is a convex portion in the shape of a groove, a line is formedin the pattern 12C.

Now, materials with flowability will be described.

The material with flowability used for forming an organic film is, forexample, an aromatic polymer having aryl ether as a principal skeleton,and specific examples are FLARE and GX-3 (manufactured by Honeywell) andSiLK (manufactured by Dow Chemical).

The material with flowability used for forming an inorganic film is, forexample, HSQ (hydrogen silsquioxane) or organic SOG such as analkylsiloxane polymer, and a specific example of the HSQ is Fox(manufactured by Dow Corning) and a specific example of the organic SOGis HSG-RZ25 (manufactured by Hitachi Chemical Co., Ltd.).

The material with flowability used for forming an organic-inorganic filmis, for example, organic siloxane having an organic group such as amethyl group in a siloxane skeleton, and a specific example is HOSP(hybrid organic siloxane polymer) (manufactured by Honeywell).

The material with flowability used for forming a photo-setting resinfilm is, for example, PDGI (polydimethyl glutarimide), and a specificexample is SAL101 (manufactured by Shipley Far East).

The material with flowability used for forming a photosensitive resinfilm may be a general resist material used in the lithography.

The material with flowability used for forming a porous film is, forexample, an organic, inorganic or organic-inorganic material havingpores, a specific example of the organic material having pores is PorousFLARE (manufactured by Honeywell), a specific example of the inorganicmaterial having pores is XLK (manufactured by Dow Corning) having poresin HSQ (hydrogen silsquioxane), and specific examples of theorganic-inorganic material having pores are Nanoglass (manufactured byHoneywell) and LKD-5109 (manufactured by JSR).

When the pattern 12C obtained by solidifying and burning the flowablefilm 12A made of any of the aforementioned materials is used as aninterlayer insulating film of multilayered interconnects, an interlayerinsulating film that is dense and has a lower dielectric constant than ageneral silicon oxide film (with a dielectric constant of approximately4) can be obtained. Therefore, a film suitable to a semiconductor devicerefined to 100 nm or less can be realized. In particular, when a porousfilm is used, an interlayer insulating film with a very low dielectricconstant of 2 or less can be realized.

Although the aforementioned materials are materials for an insulatingfilm, the present invention is applicable not only to a method forforming an insulating film but also to a method for forming a conductivepolymer film or metal film.

(Embodiment 2)

A pattern formation method according to Embodiment 2 of the inventionwill now be described with reference to FIGS. 2A through 2E.

Since the basic process sequence of Embodiment 2 is almost the same asthat of Embodiment 1, a difference from that of Embodiment 1 will beprincipally described below.

First, in the same manner as in Embodiment 1, a flowable film 12A isformed on a substrate 11 as shown in FIG. 2A. Thereafter, as shown inFIG. 2B, a pressing member 13 is pressed against the flowable film 12A,so as to transfer irregularities of the pressing face onto the flowablefilm 12A and planarize the whole top face of the flowable film 12Aexcluding the transferred irregularities.

Next, as shown in FIG. 2C, with the pressing member 13 pressed againstthe flowable film 12A, the flowable film 12A is annealed at a firsttemperature (T1), so as to cause a chemical reaction within the flowablefilm 12A. Thus, the flowable film 12A is solidified, thereby forming asolidified film 12B having the transferred irregularities and a flat topface.

Then, as shown in FIG. 2D, after moving the pressing member 13 away fromthe solidified film 12B, the solidified film 12B is annealed at a secondtemperature (T2) higher than the first temperature (T1) for burning thesolidified film 12B, thereby forming a pattern 12C made of the burntsolidified film 12B. Thereafter, the temperature of the pattern 12C islowered to approximately room temperature. In this manner, as shown inFIG. 2E, the pattern 12C having a concave portion 15 formed through thetransfer of a convex portion 14 of the pressing member 13 is formed.

A difference between Embodiment 1 and Embodiment 2 is that thesolidified film 12B is burnt with the pressing face of the pressingmember 13 pressed against the solidified film 12B in Embodiment 1 whileit is burnt with the pressing face of the pressing member 13 moved awayfrom the solidified film 12B in Embodiment 2. Accordingly, in Embodiment2, it is necessary to perform the annealing with a hot plate in thesolidifying process but the annealing can be performed with a hot plateor a furnace in the burning process.

Embodiment 2 is more effective than Embodiment 1 in the case where asolidified film largely outgassing is annealed in the burning process(the process for forming a pattern). In a general film, theconcentration of a remaining solvent in the film can be controlledthrough the pre-bake, and therefore, the film minimally outgases in theburning process, but depending upon the composition of the film, it mayoutgas in the burning process where the annealing is performed at acomparatively high temperature. In such a case, there may arise aproblem of uniformity or stability of the pattern 12C when the burningprocess of Embodiment 1 is performed, and hence, the burning process ofEmbodiment 2 is preferably performed. In particular, this effect isexhibited when the pattern 12C is a porous film. In a porous film, mostof the basic structure of the film is formed through the annealingperformed at the first temperature (T1) in the solidifying process, anda pore forming material added for forming pores is vaporized through theannealing performed at the second temperature (T2) in the burningprocess. Therefore, the burning process of Embodiment 2 in which thefilm is burnt with the pressing member 13 moved away from the solidifiedfilm 12B is suitable. Even in a porous film, if it is such an optimalfilm in which the basic skeleton of the film is formed and most of apore forming material is vaporized in the solidifying process, a goodpattern 12C can be obtained even by employing the burning process ofEmbodiment 1.

In Embodiment 1 or 2, the annealing temperature of the burning process(the second temperature) is set to be higher than the annealingtemperature of the solidifying process (the first temperature). In thecase where the pattern 12C is used as an insulating film of asemiconductor device, the annealing temperature of the solidifyingprocess (the first temperature) is preferably approximately 150° C.through 300° C., and the annealing temperature of the burning process(the second temperature) is preferably approximately 350° C. through450° C.

Next, a difference between a conventional pattern formation method andthe present pattern formation method will be described with reference toFIGS. 3A and 3B.

As shown in FIG. 3A, in the conventional pattern formation method, afilm having irregularities is formed through one annealing in a filmcuring process performed after pressing a pressing member (a mold). Onthe contrary, as shown in FIG. 3B, in the present pattern formationmethod, after pressing the pressing member (a mold) (after thetransferring process), a pattern 12C having transferred irregularitiesis formed through the annealing performed in the two stages in thesolidifying process and the burning process.

<EXAMPLE 1>

As a method for forming a flowable film used in Embodiment 1 or 2, afirst spin coating method will now be described with reference to FIGS.4A through 4C.

First, as shown in FIG. 4A, after holding a substrate 21 through vacuumadsorption on a rotatable stage 20, an appropriate amount of material 23with flowability is dropped on the substrate 21, and thereafter, thestage 20 is rotated. Alternatively, as shown in FIG. 4B, after holding asubstrate 21 through vacuum adsorption on a rotatable stage 20, amaterial 23 with flowability is supplied from a dropping nozzle 24 ontothe substrate 21 while rotating the stage 20 together with the substrate21.

In this manner, a flowable film 22 is formed on the substrate 21 asshown in FIG. 4C.

In either of the method shown in FIG. 4A and the method shown in FIG.4B, when the viscosity of the material 23 with flowability and therotation speed of the stage 20 are optimized, the flowable film 22 canattain hardness suitable for the process for transferring theirregularities of the pressing member 13 (see FIG. 1B or 2B) onto theflowable film 22.

It is noted that the method of Example 1 is suitable to a case where theflowable film 22 is formed in a comparatively large thickness.

<EXAMPLE 2>

As a method for forming a flowable film used in Embodiment 1 or 2, asecond spin coating method will now be described with reference to FIGS.5A and 5B.

First, as shown in FIG. 5A, after holding a substrate 21 through vacuumadsorption on a rotatable stage 20, a material 26 with flowability issupplied in the form of a shower or spray from a spray nozzle 25 ontothe substrate 21 while rotating the stage 20 together with the substrate21.

After supplying a desired amount of material 26 with flowability, thestage 20 is continuously rotated for a predetermined period of time.Thus, a flowable film 22 is formed on the substrate 21 as shown in FIG.5B.

The method of Example 2 is suitable to a case where the flowable film 22is formed in a comparatively small thickness.

<EXAMPLE 3>

As a method for forming the flowable film used in Embodiment 1 or 2, amicroscopic spraying method will now be described with reference toFIGS. 6A and 6B.

First, as shown in FIG. 6A, a material 28 with flowability is suppliedfrom a dropping nozzle 27 onto a substrate 21 by a given amount at atime while moving the substrate 21 along one of the two perpendiculardirections of the two-dimensional rectangular coordinate system, forexample, along the lateral direction of FIG. 6A and moving the droppingnozzle 27 along the other of the two perpendicular directions, forexample, along the longitudinal direction of FIG. 6A. In other words, anoperation for moving the substrate 21 by a given distance toward theleftward direction in FIG. 6A and stopping it is repeatedly performed,and while the substrate 21 is stopped, the material 28 with flowabilityis supplied from the dropping nozzle 27 onto the substrate 21 by a givenamount at a time while moving the dropping nozzle 27 along thelongitudinal direction in FIG. 6A.

In this manner, a flowable film 22 is formed on the substrate 21 asshown in FIG. 6B.

In the method of Example 3, the thickness of the flowable film 22 can becontrolled over a range from a small thickness to a large thickness byadjusting the amount of material 28 with flowability supplied from thedropping nozzle 27 and the moving rate of the dropping nozzle 27.

Also, the degree of the flowability of the flowable film 22 can bechanged by adjusting the viscosity of the material 28 with flowabilitysupplied from the dropping nozzle 27.

Furthermore, the process speed can be controlled by adjusting the numberof dropping nozzles 27.

<EXAMPLE 4>

As a method for forming a flowable film used in Embodiment 1 or 2, arotation roller method will now be described with reference to FIGS. 7Aand 7B.

As shown in FIGS. 7A and 7B, with a material 30 with flowabilityuniformly adhered onto the peripheral face of a rotation roller 29, therotation roller 29 is rotationally moved on the surface of a substrate21.

In this manner, the material 30 with flowability is adhered onto thesurface of the substrate 21, and hence, a flowable film 22 is formed onthe substrate 21 as shown in FIG. 7B.

In the method of Example 4, the thickness of the flowable film 22 can becontrolled by adjusting the distance between the rotation roller 29 andthe substrate 21 and a force for pressing the rotation roller 29 againstthe substrate 21.

Also, the method of Example 4 is suitable to a case where the material30 with flowability is in the form of a highly viscous liquid or a gel.

(Embodiment 3)

A pattern formation method according to Embodiment 3 will now bedescribed with reference to FIGS. 8A through 8C and 9A through 9C.

In Embodiment 3, methods for selectively removing a peripheral portionof the flowable film obtained in Embodiment 1 or 2 are described.Specifically, in a first method, the peripheral portion is removed bysupplying a solution for dissolving the flowable film to the peripheralportion of the flowable film while rotating the substrate on which theflowable film is formed, and in a second method, the peripheral portionof the flowable film is modified by irradiating the peripheral portionwith light and thereafter the modified peripheral portion is removed.

In Embodiment 1 or 2, the flowable film is formed over the whole surfaceof the substrate, namely, also on a peripheral portion of the substrate.However, it is sometimes necessary to mechanically hold the peripheralportion of the substrate.

Embodiment 3 is devised for overcoming such a problem, and since theperipheral portion of the flowable film is selectively removed inEmbodiment 3, the peripheral portion of the substrate can be easilymechanically held.

Now, the first method for selectively removing the peripheral portion ofa flowable film 22 will be described with reference to FIGS. 8A through8C.

First, as shown in FIG. 8A, after a substrate 21 on which the flowablefilm 22 is formed is held through vacuum adsorption on a rotatable stage20, the stage 20 is rotated for rotating the flowable film 22, a releasesolution 33 is supplied from a first nozzle 31 to the peripheral portionof the flowable film 22 and a release solution 34 is supplied from asecond nozzle 32 to the back surface of the peripheral portion of thesubstrate 21.

Thus, as shown in FIG. 8B, the peripheral portion of the flowable film22 can be removed as well as the material with flowability having beenadhered onto the peripheral portion of the back surface of the substrate21 can be removed.

Next, while continuously rotating the stage 20, the supply of therelease solutions 33 and 34 is stopped, so as to dry the flowable film22. In this manner, as shown in FIG. 8C, the flowable film 22 whoseperipheral portion has been selectively removed can be obtained.

It is noted that the first method is preferably performed before thetransferring process for the flowable film 22.

Since the peripheral portion of the flowable film 22 is removed whilerotating the stage 20 together with the flowable film 22 in the firstmethod, this method is suitable when the plane shape of the substrate 21is in the shape of a circle or a polygon with a large number ofvertexes.

Now, the second method for selectively removing the peripheral portionof a flowable film 22 will be described with reference to FIGS. 9Athrough 9C.

First, as shown in FIG. 9A, after a substrate 21 on which the flowablefilm 22 is formed is held through vacuum adsorption on a rotatable stage20, the stage 20 is rotated for rotating the flowable film 22, and theperipheral portion of the flowable film 22 is irradiated with light 36emitted from a photoirradiation device 35, so as to modify theperipheral portion by causing a photochemical reaction in the peripheralportion (irradiated portion) of the flowable film 22. The light 36 usedin this case is preferably UV or light of a shorter wavelength than UV.

Next, as shown in FIG. 9B, after stopping the rotation of the stage 20together with the flowable film 22, a solution 37 such as a developer issupplied over the flowable film 22. Thus, the peripheral portion of theflowable film 22 having been modified is dissolved in the solution 37,and hence, the peripheral portion of the flowable film 22 can beselectively removed.

Then, as shown in FIG. 9C, the stage 20 is rotated together with theflowable film 22 again, so as to remove the solution 37 remaining on theflowable film 22 to the outside by using centrifugal force. In thiscase, while or after removing the solution 37, a rinsing solution ispreferably supplied onto the flowable film 22 so as to remove thesolution 37 still remaining. In this manner, the flowable film 22 whoseperipheral portion has been selectively removed can be obtained.

It is noted that the second method is preferably performed before thetransferring process for the flowable film 22.

Since the peripheral portion of the flowable film 22 is selectivelyirradiated with the light 36 in the second method, this method isapplicable not only when the plane shape of the substrate 21 is in theshape of a circle or a polygon with a large number of vertexes but alsowhen it is in the shape of a polygon with a small number of vertexessuch as a triangle or a rectangle.

(Embodiment 4)

A pattern formation method according to Embodiment 4 of the inventionwill now be described with reference to FIGS. 10A, 10B, 11A and 11B.

In Embodiment 4, a preferable method for transferring the irregularitiesonto the flowable film obtained in Embodiment 1 or 2 is described, andin this method, a plurality of distances between the surface of thesubstrate or the stage and the pressing face of the pressing member aremeasured and the flowable film is pressed in such a manner that theseplural distances are equal to one another.

First, as shown in FIG. 10A, after forming a flowable film 42 on asubstrate 41 by the method of Embodiment 1 or 2, a pressing member 43having irregularities and a plurality of distance sensors 44 on itspressing face is used for transferring the irregularities of thepressing member 43 onto the flowable film 42. In Embodiment 4, theoutside dimension of the stage 20 (see FIG. 4C or 5B) is preferablylarger than that of the substrate 41.

In this case, a plurality of distances between the surface of thesubstrate 41 or the surface of the stage 20 (see FIG. 4C or 5B) on whichthe substrate 41 is placed and the pressing face of the pressing member43 are measured with the plural distance sensors 44, and theirregularities of the pressing member 43 are transferred onto theflowable film 42 by pressing the flowable film 42 with the pressingmember 43 in such a manner that the plural distances are equal to oneanother. Specifically, information of the plural distances measured withthe plural distance sensors 44 is fed back to pressing means forpressing the pressing member 43, so that the flowable film 42 can bepressed in such a manner that the plural distances are equal to oneanother. The feedback control may be executed by using a computer. Also,in measuring the plural distances between the surface of the substrate41 or the surface of the stage 20 (see FIG. 4C or 5B) on which thesubstrate 41 is placed and the pressing face of the pressing member 43,each distance is preferably measured by measuring capacitance per unitarea in the corresponding measurement position. Thus, the pluraldistances can be easily and definitely measured.

Now, the method for measuring the plural distances between the surfaceof the substrate 41 and the pressing face of the pressing member 43 willbe described with reference to FIG. 10B.

In FIG. 10B, a, b, c, . . . and q denote positions where the distancesensors 44 are respectively provided. The positions a through q arepreferably optimized in accordance with the mechanism of the pressingmember 43 so as to be set to positions where the distances between thesurface of the substrate 41 or the surface of the stage where thesubstrate 41 is placed and the surface of the flowable film 42 can beefficiently measured. For example, the sensor positions a through i atthe center are suitable to measure the distances between the surface ofthe substrate 41 and the surface of the flowable film 42, and the sensorpositions j through q in the peripheral portion are suitable to measurethe distances between the surface of the stage where the substrate 41 isplaced and the surface of the flowable film 42.

Accordingly, merely the distances between the surface of the substrate41 and the surface of the flowable film 42 may be measured with thedistance sensors 44 provided in the sensor positions a through i alone,merely the distances between the surface of the stage where thesubstrate 41 is placed and the surface of the flowable film 42 may bemeasured with the distance sensors 44 provided in the sensor positions jthrough q alone, or the distances between the surface of the substrate41 and the surface of the flowable film 42 and the distances between thesurface of the stage where the substrate 41 is placed and the surface ofthe flowable film 42 may be measured with the distance sensors 44provided in the sensor positions a through q.

Alternatively, in the case where the irregularities of the pressing faceof the pressing member 44 can be finely adjusted, after the distancesbetween the surface of the substrate 41 and the surface of the flowablefilm 42 are adjusted with the distance sensors 44 provided in the sensorpositions a through i, the distances between the surface of thesubstrate 41 and the surface of the flowable film 42 may be adjustedwith the distance sensors 44 provided in the sensor positions j throughq. Thus, more highly accurate flatness can be realized. It is noted thatthe number and the positions of the distance sensors 44 may be optimizedin accordance with a desired degree of flatness.

In Embodiment 1, it is significant but is not easy to equalize adistance of the surface of the flowable film 12A from the surface of thesubstrate 11. In other words, in Embodiment 1, the distance of thesurface of the flowable film 12A from the surface of the substrate 11can be made uniform by previously setting the distance between thesurface of the substrate 11 and the pressing face of the pressing member13 to be uniform. However, in this method, it is necessary to set thedistance between the surface of the substrate 11 and the pressing faceof the pressing member 13 to be uniform every given period of time,namely, every time the pressing face of the pressing member 13 haspressed a given number of flowable films 12A.

However, in Embodiment 4, the distance of the surface of the flowablefilm 42 from the surface of the substrate 41 can be always uniform, andhence, an operation for making the distance between the surface of thesubstrate 41 and the pressing face of the pressing member 43 uniformevery given period of time can be omitted.

The process for adjusting the distance between the surface of thesubstrate 41 and the pressing face of the pressing member 43 to beuniform may be performed before, while or after pressing the flowablefilm 42 with the pressing member 43.

FIG. 11A shows a cross-section of the flowable film 42 obtained when thedistance between the pressing face of the pressing member 43 and thesurface of the substrate 41 is ununiform, and FIG. 11B shows across-section of the flowable film 42 obtained when the distance betweenthe pressing face of the pressing member 43 and the surface of thesubstrate 41 is kept uniform. In FIGS. 11A and 11B, a reference numeral45 denotes a pressure plate for applying a pressure to the pressingmember 43.

As is understood from comparison between FIGS. 11A and 11B, when theflowable film 42 is pressed with the distance between the pressing faceof the pressing member 43 and the surface of the substrate 11 keptuniform, the top face of the flowable film 42 can be planarized with thedistance of the flowable film 42 from the surface of the substrate 41kept uniform.

(Embodiment 5)

A pattern formation method according to Embodiment 5 will now bedescribed with reference to FIGS. 12A and 12B.

In the method of Embodiment 5, a flowable film 52A is solidified byannealing the flowable film 52A while irradiating it with light.

As shown in FIG. 12A, while pressing, with a pressure plate 54, apressing face of a pressing member 53, which is made of a lighttransmitting material such as quartz and has irregularities on itspressing face, against the flowable film 52A formed on a substrate 51,so as to transfer the irregularities of the pressing member 53 onto theflowable film 52A, the flowable film 52A is irradiated with light andannealed. The light used for the irradiation is, when the flowable film52A is solidified principally through a photochemical reaction,preferably UV or light of a shorter wavelength than UV, and when theflowable film 52A is solidified principally through a thermal chemicalreaction, preferably infrared light.

Thus, the flowable film 52A is solidified through the photochemicalreaction or the thermal chemical reaction, resulting in giving asolidified film 52B as shown in FIG. 12B.

The method for solidifying the flowable film 52A principally through thephotochemical reaction is suitable to a film of a photo-setting resin,such as a photosensitive resin film like a photoresist used in thelithography. Also, the method for solidifying the flowable film 52Aprincipally through the thermal chemical reaction is suitable to anorganic film, an organic-inorganic film or an inorganic film made of achemically amplified material composed of a material for generating anacid or a base through irradiation with light and a base polymersolidified by an acid or a base.

(Embodiment 6)

A method for forming a semiconductor device according to Embodiment 6will now be described with reference to FIGS. 13A through 13D and 14Athrough 14D.

Although not shown in the drawings, after forming an interlayerinsulating film on a semiconductor substrate, a lower buriedinterconnect is formed in an upper portion of the interlayer insulatingfilm, and then, a diffusion preventing film is formed on the lowerburied interconnect and the interlayer insulating film. Thus, asubstrate 61 having the interlayer insulating film, the lower buriedinterconnect and the diffusion preventing film on the semiconductorsubstrate is obtained. In this case, the shape of the substrate 61 isnot limited to a plane shape. The diffusion preventing film has afunction to prevent a metal included in the lower buried interconnectfrom diffusing into an insulating film to be formed on the buriedinterconnect.

Next, as shown in FIG. 13A, in the same manner as in Embodiment 1, aninsulating material with flowability in the form of a liquid or a gel issupplied over the substrate 61 by the spin coating method, themicroscopic spraying method, the rotation roller method or the like, soas to form a flowable film 62A having an insulating property. Thethickness of the flowable film 62A can be appropriately set.

The flowable film 62A may be any of the insulating films described inEmbodiment 1, namely, an organic film, an inorganic film, anorganic-inorganic film or a porous film. When such an insulating film isused, the resultant insulating film attains a lower dielectric constantthan a general silicon oxide film, and thus, an insulating film suitableto a semiconductor device refined to 100 nm or less can be realized. Inparticular, when a porous film is used, an insulating film with a verylow dielectric constant of 2 or less can be realized.

Next, as shown in FIG. 13B, after a pressing member 63 having a pressingface with convex portions 64 in the shape of dots or lines is broughtinto contact with the surface of the flowable film 62A, a pressure isapplied to the pressing member 63 so as to transfer the convex portions64 onto the surface of the flowable film 62A for forming concaveportions thereon and to planarize the top face of the flowable film 62Aexcluding the concave portions. In other words, the top face excludingthe concave portions of the flowable film 62A is made to be placed atthe uniform height from the surface of the substrate 61.

Then, as shown in FIG. 13C, the substrate 61 together with the flowablefilm 62A are annealed at a first temperature (T1) so as to cause athermal chemical reaction in the insulating material. Thus, the flowablefilm 62A is solidified to form a solidified film 62B with the concaveportions. In the solidifying process, any of the methods of Embodiments1 through 4 suitable to the characteristics of the flowable film 62A maybe selected.

Next, as shown in FIG. 13D, in the same manner as in Embodiments 1 and2, the solidified film 62B is annealed at a second temperature (T2)higher than the first temperature (T1) for burning the solidified film62B, so as to form a pattern 62C. Thereafter, after the temperature ofthe pattern 62C is lowered to a temperature range from approximately100° C. to room temperature, the pressing member 63 is moved away fromthe pattern 62C and the temperature of the pattern 62C is loweredultimately to room temperature. In this manner, as shown in FIG. 14A,the pattern 62C having concave portions 65 in the shape of a hole orgroove and having a flat top face excluding the concave portions 65 isobtained.

Then, as shown in FIG. 14B, the pattern 62C is subjected to etch backprocess by dry etching. Thus, portions of the pattern 62C remaining onthe bottoms of the concave portions 65 are removed through the etch backprocess, and hence, holes or interconnect grooves corresponding to theconcave portions 65 are obtained. This etch back process is preferablyanisotropic dry etching. Thus, the dimensional change of the pattern 62Ccan be suppressed to be minimum and the pattern 62C having the holes orinterconnect grooves in a good shape can be realized.

Thereafter, the diffusion preventing film (not shown in the drawing) issubjected to the anisotropic dry etching, so as to expose the upper faceof the lower metal interconnect (not shown in the drawing) formed belowthe diffusion preventing film. Through the etch back process. and thedry etching of the diffusion preventing film, the lower metalinterconnect is exposed in the concave portions 65 corresponding to theholes or interconnect grooves.

In the case where the pattern 62C is made of an insulating film apartfrom an organic film, an etching gas for use in the etch back processmay be a gas including fluorine such as a CF₄ gas or a CHF₃ gas, a mixedgas of a gas including fluorine and an oxygen gas, an ammonia gas or thelike. In the case where the pattern 62C is made of an organic film, theetching gas may be a mixed gas of an oxygen gas and a nitrogen gas, amixed gas of a nitrogen gas and a hydrogen gas, an ammonia gas or thelike.

Next, as shown in FIG. 14C, a metal film 66A is deposited over thepattern 62C having the concave portions 65 corresponding to the holes orinterconnect grooves so as to fill the concave portions 65. In general,before depositing the metal film 66A, a barrier metal layer of Ta or TaNis deposited on the concave portions 65 by the sputtering, the CVD orthe like. Also, the metal film 66A is deposited by the plating methodusing, as a seed, a seed layer previously formed by the sputtering. Itis noted that the metal film 66A may be deposited by the CVD instead ofthe plating method. Copper is generally used as the metal film 66A, andapart from copper, metal that can be deposited by the plating method andhas low resistance, such as gold, silver or platinum, is preferablyused.

Then, as shown in FIG. 14D, an unnecessary portion of the metal film66A, namely, a portion thereof exposed above the pattern 62C, is removedby the CMP. Thus, a plug or an upper metal interconnect 66B made of themetal film 66A is formed in each concave portion 65.

In Embodiment 6, when the convex portions 64 provided on the pressingface of the pressing member 63 are in the shape of columns (dots), theconcave portions 65 corresponding to holes are formed in the pattern62C, and when the convex portions 64 are in the shape of lines, theconcave portions 65 corresponding to interconnect grooves are formed inthe pattern 62C. Therefore, the plug or upper metal interconnect 66B canbe formed in the pattern 62C by the single damascene method.

Although not shown in the drawings, when the aforementioned proceduresare repeated, a multilayered interconnect structure including, in eachlayer, the interlayer insulating film of the pattern 62C and the plug orupper metal interconnect 66B can be formed.

Since the interlayer insulating film made of the pattern 62C with noglobal level difference can be formed in Embodiment 6, localconcentration of film stress can be released, resulting in improving thereliability of the multilayered interconnects.

Also, in the case where a mask pattern is formed on the interlayerinsulating film made of the pattern 62C by the lithography, degradationof a focal depth margin derived from a level difference can besuppressed. Therefore, as compared with conventional technique, aprocess margin (process window) can be increased, resulting in forming ahighly accurate semiconductor device.

In the case where a film largely outgassing in the burning process isused as the flowable film 62A in Embodiment 6, the burning process ofEmbodiment 2 is more effectively employed than that of Embodiment 1. Inthe case where the flowable film 62A is made of a general film, theconcentration of a solvent remaining in the film can be controlledthrough the pre-bake, and hence, the film minimally outgases in theburning process. However, the film may largely outgas in the burningprocess where the film is annealed at a comparatively high temperaturedepending upon its composition in some cases. In such a case, when theburning process of Embodiment 1 is employed, there arises a problem ofuniformity or stability in the pattern 62C, and hence, the burningprocess of Embodiment 2 is preferably employed.

In particular, when the pattern 62C is made of a porous film, theburning process of Embodiment 2 is effectively employed. In a porousfilm, most of the basic structure of the film is formed in thesolidifying process, and a pore forming material added for forming poresis evaporated in the following burning process. Therefore, the burningprocess of Embodiment 2 where the film is burnt with the pressing member63 moved away from the solidified film 62B is suitable. However, even inusing a porous film, when a material in which the basic skeleton of thefilm is formed and a pore forming material is vaporized simultaneouslyin the solidifying process is used, a good pattern 62C can be obtainedeven by employing the burning process of Embodiment 1.

Since the pattern 62C is used as an insulating film of a semiconductordevice in Embodiment 6, the annealing temperature of the solidifyingprocess (the first temperature) is preferably approximately 150° C.through 300° C., and the annealing temperature of the burning process(the second temperature) is preferably approximately 350° C. through450° C.

(Embodiment 7)

A method for forming a semiconductor device according to Embodiment 7will now be described with reference to FIGS. 15A through 15D and 16Athrough 16D.

Although not shown in the drawings, after forming an interlayerinsulating film on a semiconductor substrate, a lower buriedinterconnect is formed in an upper portion of the interlayer insulatingfilm, and then, a diffusion preventing film is formed on the lowerburied interconnect and the interlayer insulating film. Thus, asubstrate 71 having the interlayer insulating film, the lower buriedinterconnect and the diffusion preventing film on the semiconductorsubstrate is obtained. In this case, the shape of the substrate 71 isnot limited to a plane shape.

Next, as shown in FIG. 15A, in the same manner as in Embodiment 1, aninsulating material with flowability in the form of a liquid or a gel issupplied over the substrate 71 by the spin coating method, themicroscopic spraying method, the rotation roller method or the like, soas to form a flowable film 72A having an insulating property. Theflowable film 72A may be any of the insulating films described inEmbodiment 1, namely, an organic film, an inorganic film, anorganic-inorganic film or a porous film.

Next, as shown in FIG. 15B, after a pressing member 73 having a pressingface with convex portions 74 in the shape of lines having dots thereonis brought into contact with the surface of the flowable film 72A, apressure is applied to the pressing member 73 so as to transfer theconvex portions 74 onto the surface of the flowable film 72A for formingconcave portions thereon and to planarize the top face excluding theconcave portions.

Then, as shown in FIG. 15C, the substrate 71 together with the flowablefilm 72A are annealed at a first temperature (T1) so as to cause athermal chemical reaction in the insulating material. Thus, the flowablefilm 72A is solidified to form a solidified film 72B with the concaveportions. In the solidifying process, any of the methods of Embodiments1 through 4 suitable to the characteristics of the flowable film 72A maybe selected.

Next, as shown in FIG. 15D, in the same manner as in Embodiments 1 and2, the solidified film 72B is annealed at a second temperature (T2)higher than the first temperature (T1) for burning the solidified film72B, so as to form a pattern 72C. Thereafter, after the temperature ofthe pattern 72C is lowered to a temperature range from approximately100° C. to room temperature, the pressing member 73 is moved away fromthe pattern 72C and the temperature of the pattern 72C is loweredultimately to room temperature. In this manner, as shown in FIG. 16A,the pattern 72C having concave portions 75 consisting of interconnectgrooves 75 a and holes 75 b present below the interconnect grooves 75 aand having a flat top face excluding the concave portions 75 isobtained.

Then, as shown in FIG. 16B, the pattern 72C is subjected to etch backprocess by dry etching. Thus, portions of the pattern 72C remaining onthe bottoms of the concave portions 75 are removed through the etch backprocess, and hence, the concave portions 75 integrally consisting of theinterconnect grooves 75 a and the holes 75 b are obtained.

Thereafter, the diffusion preventing film (not shown in the drawing) issubjected to the anisotropic dry etching, so as to expose the upper faceof the lower metal interconnect (not shown in the drawing) formed belowthe diffusion preventing film. Through the etch back process and the dryetching of the diffusion preventing film, the lower metal interconnectis exposed in the concave portions 75 consisting of the interconnectgrooves 75 a and the holes 75 b.

Next, as shown in FIG. 16C, a metal film 76A is deposited over thepattern 72C having the concave portions 75 so as to fill the concaveportions 75. In general, before depositing the metal film 76A, a barriermetal layer of Ta or TaN is deposited on the concave portions 75 by thesputtering, the CVD or the like.

Then, as shown in FIG. 16D, an unnecessary portion of the metal film76A, namely, a portion thereof exposed above the pattern 72C, is removedby the CMP. Thus, upper metal interconnects 76B and plugs 76C made ofthe metal film 76A are formed in the concave portions 75.

In Embodiment 7, since the convex portions 74 provided on the pressingface of the pressing member 73 are in the shape of lines and dots, theconcave portions 75 consisting of the interconnect grooves 75 a and theholes 75 b are formed in the pattern 72C. Therefore, the upper metalinterconnects 76B and the plugs 76C can be formed by the dual damascenemethod.

Although not shown in the drawings, when the aforementioned proceduresare repeated, a multilayered interconnect structure including, in eachlayer, the interlayer insulating film of the pattern 72C, the uppermetal interconnects 76B and the plugs 76C can be formed.

1. A pattern formation method comprising the steps of: forming aflowable film made of a material with flowability; forming at least oneof a concave portion and a convex portion provided on a pressing face ofa pressing member onto said flowable film by pressing said pressingmember against said flowable film; forming a solidified film bysolidifying said flowable film, onto which said at least one of aconcave portion and a convex portion has been transferred, throughannealing at a first temperature with said pressing member pressedagainst said flowable film; and forming a pattern made of saidsolidified film burnt by annealing at a second temperature higher thansaid first temperature.
 2. The pattern formation method of claim 1,wherein said first temperature is approximately 150° C. throughapproximately 300° C.
 3. The pattern formation method of claim 1,wherein said second temperature is approximately 350° C. throughapproximately 450° C.
 4. The pattern formation method of claim 1,wherein said material with flowability is an insulating material.
 5. Thepattern formation method of claim 1, wherein said material withflowability is in the form of a liquid or a gel.
 6. The patternformation method of claim 1, wherein in the step of forming a flowablefilm, said flowable film is formed on a substrate by supplying saidmaterial with flowability onto said substrate rotated.
 7. The patternformation method of claim 1, wherein in the step of forming a flowablefilm, said flowable film is formed on a substrate by supplying saidmaterial with flowability onto said substrate and rotating saidsubstrate after the supply.
 8. The pattern formation method of claim 1,wherein in the step of forming a flowable film, said flowable film isformed on a substrate by supplying, in the form of a shower or a spray,said material with flowability onto said substrate rotated.
 9. Thepattern formation method of claim 1, wherein in the step of forming aflowable film, said flowable film is formed on a substrate by supplyingsaid material with flowability from a fine spray vent of a nozzle ontosaid substrate with said nozzle having said fine spray vent and saidsubstrate relatively moved along plane directions.
 10. The patternformation method of claim 1, wherein in the step of forming a flowablefilm, said flowable film is formed on a substrate by supplying saidmaterial with flowability having been adhered to a surface of a rolleronto said substrate with said roller rotated.
 11. The pattern formationmethod of claim 1, further comprising, between the step of forming aflowable film and the step of forming at least one of a concave portionand a convex portion onto said flowable film, a step of selectivelyremoving a peripheral portion of said flowable film.
 12. The patternformation method of claim 11, wherein the step of selectively removing aperipheral portion of said flowable film is performed by supplying asolution for dissolving said material with flowability onto saidperipheral portion of said flowable film with said flowable filmrotated.
 13. The pattern formation method of claim 11, wherein the stepof selectively removing a peripheral portion of said flowable film isperformed by modifying said peripheral portion of said flowable filmthrough irradiation with light and removing said modified peripheralportion.
 14. The pattern formation method of claim 1, wherein saidflowable film is formed on a substrate, and in the step of forming atleast one of a concave portion and a convex portion onto said flowablefilm, a plurality of distances between a surface of said substrate andsaid pressing face are measured, and said flowable film is pressed withsaid pressing face in such a manner that said plurality of distances areequal to one another.
 15. The pattern formation method of claim 14,wherein said plurality of distances are measured by measuringcapacitance per unit area in respective measurement positions.
 16. Thepattern formation method of claim 1, wherein said flowable film isformed on a substrate, and in the step of forming at least one of aconcave portion and a convex portion onto said flowable film, aplurality of distances between a surface of a stage where said substrateis placed and said pressing face are measured, and said flowable film ispressed with said pressing face in such a manner that said plurality ofdistances are equal to one another.
 17. The pattern formation method ofclaim 1, wherein said pressing face of said pressing member has ahydrophobic property.
 18. The pattern formation method of claim 1,wherein said material with flowability is a photo-setting resin, and thestep of forming a solidified film includes a sub-step of irradiatingsaid flowable film with light.
 19. The pattern formation method of claim1, wherein said material with flowability is an organic material, aninorganic material, an organic-inorganic material, a photo-setting resinor a photosensitive resin.
 20. The pattern formation method of claim 1,wherein said pattern is a porous film.
 21. The pattern formation methodof claim 1, wherein in the step of forming a pattern, said solidifiedfilm is annealed at said second temperature with said pressing facepressed against said solidified film.
 22. The pattern formation methodof claim 1, wherein in the step of forming a pattern, said solidifiedfilm is annealed at said second temperature with said pressing facemoved away from said solidified film.
 23. A method for forming asemiconductor device comprising the steps of: forming a flowable filmmade of an insulating material with flowability; forming a convexportion provided on a pressing face of a pressing member onto saidflowable film by pressing said pressing member against said flowablefilm; forming a solidified film by solidifying said flowable film, ontowhich said convex portion has been transferred, through annealing at afirst temperature with said pressing member pressed against saidflowable film; forming a pattern having a concave portion in the shapecorresponding to said convex portion and made of said solidified filmburnt by annealing at a second temperature higher than said firsttemperature; and forming at least one of a metal interconnect and a plugby filling said concave portion with a conductive material.
 24. Themethod for forming a semiconductor device of claim 23, wherein saidfirst temperature is approximately 150° C. through approximately 300° C.25. The method for forming a semiconductor device of claim 23, whereinsaid second temperature is approximately 350° C. through approximately450° C.
 26. The method for forming a semiconductor device of claim 23,wherein said material with flowability is a photo-setting resin, and thestep of forming a flowable film includes a sub-step of irradiating saidflowable film with light.
 27. The method for forming a semiconductordevice of claim 23, wherein said material with flowability is an organicmaterial, an inorganic material, an organic-inorganic material, aphoto-setting resin or a photosensitive resin.
 28. The method forforming a semiconductor device of claim 23, wherein in the step offorming a pattern, said solidified film is annealed at said secondtemperature with said pressing face pressed against said solidifiedfilm.
 29. The method for forming a semiconductor device of claim 23,wherein in the step of forming a pattern, said solidified film isannealed at said second temperature with said pressing face moved awayfrom said solidified film.
 30. The method for forming a semiconductordevice of claim 23, wherein said pattern is a porous film.
 31. Themethod for forming a semiconductor device of claim 23, wherein saidpattern has a dielectric constant of approximately 4 or less.
 32. Themethod for forming a semiconductor device of claim 23, furthercomprising, after the step of forming a pattern and before the step offorming at least one of a metal interconnect and a plug, a step ofremoving a portion of said pattern remaining on a bottom of said concaveportion by etching.